Prior art systems used to filter machine tool working fluids conventionally include an electric motor driven pump, one or more dirty side tank(s) for collecting the contaminated working fluid, a filter, a clean side tank or compartment, and (usually) a second pump to return the clean filtrate back to one or more machine tools. Representative systems are disclosed in U.S. Pat. No. 2,276,824 to Carruthers and U.S. Pat. No. 4,282,094 to Mitchell.
The industrial coolant filtering systems in U.S. Pat. No. 4,865,724 to Brandt et al., U.S. Pat. No. 5,417,849 to McEwen et al., and U.S. Pat. No. 6,485,634 to Warren et al. share these characteristics. Also described in the prior art are auxiliary and/or portable filter systems for recycling machine tool working fluids such as U.S. Pat. No. 4,361,488 to White et al. and U.S. Pat. No. 5,417,851 to Yee.
Wire EDMs (Electrical Discharge Machines) require the filtration of large volumes of the working fluid, in this case deionized H2O. The filtration systems of many wire EDMs share the basic configuration of such continuous loop filtration systems. The basic features include a dirty side pump, a dirty side tank, a filter, a clean side tank, and a clean side return pump.
To properly size the filtration requirements, a unique plumbing arrangement has evolved for EDMs. The flow path of the EDM fluid in a typical wire EDM is shown in FIG. 1. Most of the filtration systems of major wire EDM manufacturers are plumbed inside-outside, that is, the dirty fluid enters the filter thru an orifice in the end cap and exits, once filtered, thru the filter media and down the sides of the element. An advantage of this system is that contaminants are contained inside the dirty filter. At change-out, minimal spillage of dirty water occurs which would foul the clean side.
To accommodate the amount of water necessary to keep the wire EDM functioning, fairly powerful pumps are utilized. This requires high burst strength vessel(s) to encapsulate the pleated filter element(s).
The metal or high strength plastic components (end caps and wrappers) necessary to this approach are both expensive and heavy. The filter element disclosed in U.S. Pat. No. 5,935,457 to Kita et al. is of this type.
What is needed is a more user-friendly, less expensive filtration approach for wire EDMs and other fluid-filtration applications.